Quad 306 upgrades

[Jeebsy]

I recently got a Quad 306 off eBay replace my NAD c320bee (after adding a MiniDSP and a Yamaha streamer/preamp into my setup, only the NAD's power section was being used anyway).

Visually it looks fine inside, no issues with the caps, but it's probably still pushing 25 years old so I was thinking about a service/overhaul.

Quad would be the obvious place to send it, but from reading various threads on there, they only change the binding posts as standard, and anything else is only replaced if it's outside of spec.

Then there's Fidele and Redhill, who offer service and upgrade packages. Their services seem to be fairly well regarded across various forums.

I live fairly close to Fidele so could drop my amp there - their 'stage one' service and upgrade is:


Replace all electrolytic capacitors with Nichicon Audio grade capacitors
Replace Op Amp with selected low offset version of same type.
Upgrade power supply to the Op Amps
Full bench test
Replace binding posts
Adjust input sensitivity to match your pre-amplifier if required

Some people seem to think the amps could benefit from a bit of modernising, whereas others say the only thing you should change be the caps otherwise you start drifting away from the Quad sound.

Has anyone done the upgrades with Fidele or Redhill, and would you consider them to improve the sound quality? Or is it better to keep the amp as 'Quad' intended?

[walpurgis]

In standard condition the 306 is a nice sounding power amp. Quad built to a spec not a price, so no corners have been cut and making any alterations may not improve it and could devalue it, so be careful what mods are made. My personal view is that they should be serviced if need be, but the only alteration should be reducing the input sensitivity and then only if you want to use it with non Quad pre-amps.

Bear in mind that even just a service will possibly cost you what the amp is worth. You could ask Alan (Firebottle) to service it, he'd do a proper job at a very fair price and do any sensible tweaks if need be.

I've had/used many Quad power amps and the 306 is my favourite and also the best sounding to me.

[Pieoftheday]

I sent mine to Jez Arkless, no longer on here, he was also of the mind that the 306 should just be serviced and not tinkered with, hes in Northumberland I think:)

[walpurgis]

The 306 has a nice accessible interior layout, so servicing is pretty easy. Most enthusiasts could do the basics with a bit of confidence. Components sets are available at modest prices.

You may find the Dada website interesting: https://www.dadaelectronics.eu/uploads/downloads/01_Dada-Electronics-Revision-Upgrade-Manuals/Quad-306-Upgrade-Revision-Manual-V1.4.pdf

Many people install 'fancy' larger speaker terminals. There's no real need and the bigger ones can get broken off easily, the only issue with standard ones is slackening their grip over time, but they are easily replaced and available or can be crimped a bit to restore their hold on the plugs.

[southall-1998_mk2]

In standard condition the 306 is a nice sounding power amp. Quad built to a spec not a price, so no corners have been cut and making any alterations may not improve it and could devalue it, so be careful what mods are made. My personal view is that they should be serviced if need be, but the only alteration should be reducing the input sensitivity and then only if you want to use it with non Quad pre-amps.

Bear in mind that even just a service will possibly cost you what the amp is worth. You could ask Alan (Firebottle) to service it, he'd do a proper job at a very fair price and do any sensible tweaks if need be.

I've had/used many Quad power amps and the 306 is my favourite and also the best sounding to me.

Wise post, Geoff.

These lovely amps only need a sensible service to last another 25 + years. I'd never bother with upgrades.

S.

[Martyn Miles]

Amplabs of Worcester do a good job with Quad.
My 303 was serviced and and necessary parts replaced at a very competitive price,

[graham67]

Deffo have a chat with Fidele, they did a great job upgrading my 34 to 34ST spec.

[AD Audio]

Hi,
I agree with the above comments that keeping it more or less original is the way to go, but I would alter the input sensitivity. I serviced /upgraded one recently and did the following work: replaced all electrolytics, and some key capacitors and resistors in the feedback circuit as Quad did in some of their later amps, and changed the speaker terminals. The owner was very happy with the results: 'Hi David,

Hope you're good. Am loving the 306.I really think your work has made a difference - it's sounding really good and seems to gel with the Feliks as a pre-amp nicely.'

[Bencat]

I have used Fidele for two Quad 405 amps and their service and work is top class . I personally think the Quad 405 I have sound better than the standard units and could not fault the help I was given . If it was me then Fidele would be the way i would go but as has been said on here this view may not be shared by other buyers who would want a standard unit. If you are going to keep this unit and use it for some time then the Fidele upgrades make sense on a sound quality basis . If you feel you might well sell the units on then as has been said a decent service will be enough . I am sure if you speak to Fidele they can offer you a service rather than just an upgrade and as they are local that would be ideal .

[IHP]

Amplabs of Worcester do a good job with Quad.
My 303 was serviced and and necessary parts replaced at a very competitive price,

I should get my serviced 306 back from Rob tomorrow, sensible service, fair price - he really knows his stuff. An assuringly long wait too which he makes clear when you chat with him, he's a busy chap !

[IHP]

Update: I'm unable to answer your question as I haven't heard an upgraded 306, but what I would say is that a capacitor replacement service by Amplabs provides stunning results, it's like a box of fireworks !

[Bonky]

I had mine upgraded by RedHilll using components and advice from the DADA website. Very good!

[337alant]

I only changed the power supply caps in mine for a set of 63v 6800uf Kendiels, this a cracking little punchy amp.
Over the years I had this amp I had 2 of the output speaker connectors crack and fail and personally I think this type of speaker connector are crap same as the Naim ones. Any decent speaker binding post would be better

https://live.staticflickr.com/697/31949149600_b3687fbbca_c.jpg (https://flic.kr/p/QFeK5U)IMG_2941 (https://flic.kr/p/QFeK5U) by Alan Towell (https://www.flickr.com/photos/69508926@N05/), on Flickr

I mentioned this amp in a review of my power amps here
https://pinkfishmedia.net/forum/threads/diy-voyager-mono-block-build.160746/page-9#post-2510973
Alan

[Pharos]

I think that the popular WBTs are crap, the heat of my ATC amp cracked them.